The long-term goal of the investigations for which a continuation of support is sought are: (i) To develop new nutrienti for parenteral and enteral nutrition, and for nutritional treatment of diabetes. (ii) to improve our understanding of alterations of ketone body metabolism occurring in diabetes. During the next five years, we wish to achieve four specific aims: 1. To study the metabolism of the R- and S- isomers of 1,3-butanediol and 1,3-pentanediol in perfused rat organs, in live rats, dogs and monkeys. 2. To validate the non-invasive chemical biopsy of human liver, under minimal or zero load of xenobiotic. This technique will then be used: 3. To quantitate pseudoketogenesis in extrahepatic tissues, and to develop non-invasive methods for assessing the net metabolic load of ketone bodies. 4. To assess (i) the distribution of acetone metabolism between two-carbon and three-carbon pathways, and (ii) the origin of plasma acetate.